Questions with this tag should have to do with "unbricking" an Android device. Although technically the term "bricked" used to mean that a device is beyond rescue (therefore "a brick"), it is recently often used for devices that simply will not boot.
If your device will not boot, one way to restore it can be to put it into fastboot mode. The process of putting your device in a mode like this is different from every device, but it usually involves pressing a hardware button while the phone is connected with USB, and the basic point of it is the same: by putting your device in fastboot you can access your device with
fastboot devices will list all connected devices that are detected, and running
fastboot update <filename> would install something like an
update.zip. The CyanogenMod wiki article on fastboot has more information on available commands. The binary
fastboot is a part of the Android SDK.